#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define rep(i, a, b) for (int i = (a); i <= (b); i++)
#define per(i, a, b) for (int i = (a); i >= (b); i--)
#define endl '\n'
const int N = 2e5 + 5;

int n, m;
int a[N], b[N];

int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n >> m;
  rep(i, 1, n) cin >> a[i];
  rep(i, 1, m) cin >> b[i];
  sort(a + 1, a + n + 1, greater<int>());
  sort(b + 1, b + m + 1, greater<int>());
  int i = 1, j = 1;
  ll sum = 0;
  while (i <= n) {
    if (j <= m && b[j] > 0) {
      if (a[i] + b[j] > 0)
        sum += a[i++] + b[j++];
      else
        break;
    } else {
      if (a[i] > 0)
        sum += a[i++];
      else
        break;
    }
  }
  cout << sum;
  return 0;
}